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Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Toyota Mark II (X100): 1JZ-GE VVT-i Engine ECU Wiring Reference

The 1JZ-GE VVT-i ECU (200 hp, facelifted Mark II JZX100) controls fuel injection, ignition, valve timing and idle speed. I do not list a full pinout with pin numbers here, to avoid errors: it differs by market, model year and automatic transmission variant. Below is what is known reliably, along with the order for checking circuits.

Difficulty: Medium Time: 30-60 minutes (study and verification on the vehicle) Steps: 9 Tools: multimeter, test light, set of connector probes, flashlight

Part

  • 🔩 No specific part is required. When repairing ECU circuits, the most commonly needed items are: ECU connector repair kit, EFI main relay, crankshaft position sensor and camshaft position sensor, VVT-i valve (oil control valve, OCV), mass airflow sensor

Step by step

9 steps
  1. ECU location. The unit is inside the cabin, behind the lower right part of the dash, near the front passenger's feet, under the trim. It connects through several multi-pin connectors. Before disconnecting, turn the ignition off and remove the negative battery terminal.
  2. ECU power supply. Constant power (BATT) comes from the battery through a fuse. Ignition-switched power (IGSW) comes from the ignition switch. Main power +B is supplied through the EFI main relay. The EFI relay and fuses are in the fuse/relay box in the engine compartment (on the left side in the direction of travel). If the car does not start and there is no power at +B, begin with the EFI relay and its fuse.
  3. Grounds. The ECU power grounds (E01, E02) and the signal ground (E1) connect to the body and to the engine. A corroded ground causes unstable idle and false trouble codes. Check each one to body ground; resistance should be close to zero. Clean the contact points on the body and engine and apply contact grease.
  4. Sensors feeding the ECU: - Mass airflow sensor (VG signal) and intake air temperature sensor (THA). - Engine coolant temperature sensor (THW). - Throttle position sensor (VTA, IDL). - Crankshaft (NE) and camshaft (G2) sensors, which the ECU uses to determine timing. - Oxygen sensors (OX, heater HT). - Knock sensors (KNK). - Vehicle speed sensor (SPD) and A/C on signal. Sensor supply voltage is about 5 V (VC). Measure temperature sensor resistance at a known temperature and compare it with the manufacturer's table.
  5. Output circuits: - Six fuel injectors (one per cylinder, controlled by a ground from the ECU, +12 V supply through the relay). - Ignition coils: this engine has one per cylinder. The ECU sends an IGT signal, and the coil or igniter returns an IGF confirmation. If IGF is lost, the ECU usually shuts the engine off. - VVT-i valve (oil control valve, OCV) on the cylinder head. The ECU controls it with a PWM signal. Coil resistance is roughly a few ohms (check the exact value in the service manual). A stuck valve or dirty oil causes timing-related codes and a rough idle. - Idle air control valve or actuator, oxygen sensor heaters, fuel pump relay.
  6. Diagnostic connector. For this model year in Japan, there may be two types of diagnostic connectors: one in the engine compartment (near the left strut tower, with terminals TE1 and E1) and one under the dash on the driver's side (with terminals TC and CG). To read trouble codes from the flashing Check Engine light, jumper TE1-E1 (or TC-CG) with the ignition on. Codes are read by counting the flashes. To read codes with a scan tool, you need an adapter for your connector type.
  7. Circuit checking order, using the wiring diagram: - check the fuses and relays; - measure power and ground at the sensor connector with the plug disconnected; - check continuity of the wire from the sensor to the ECU pin (with the battery disconnected and the ECU connector removed); - check the resistance of the sensor itself; - only after that suspect the ECU. Do not pierce the wire insulation with a probe; use thin probes in the connector.
  8. Wire colors. Toyota color coding: the first letter is the base color, the second is the stripe color (for example, B black, W white, R red, G green, L blue, Y yellow, BR brown, V violet, O orange, P pink, LG light green, GR gray). The exact colors of specific pins depend on model year and trim, so verify against the connector itself and the pin number.
  9. Facelift specifics. Compared with the early 1JZ-GE, the late 1JZ-GE VVT-i has: VVT-i on the intake camshaft, a coil on each cylinder, and a different ECU with a different pinout. Early 1JZ-GE ECUs without VVT-i are not interchangeable. When buying a used ECU, match the full part number on the unit's case to your car's number, and also check the automatic transmission type and the market.

Common mistakes and warnings

  • Do not disconnect the ECU connector with the ignition on, and do not apply 12 V to pins at random; you can burn out the output drivers. For the exact pinout of a specific unit, use the markings on the ECU itself and measurements on the vehicle. If you have no experience with electrical systems, leave ECU circuit diagnosis to an automotive electrician.